Sharpening fixture for twist drills



March 19, 1968 c, coo Rl ER 3,373,530

SHARPENING FIXTURE FOR TWIST DRILLS Filed July 30, 1965 v Gisele 1.oopr'i iev' I flvrcIQ/OELYJ United States Patent 3,373,530 SHARPENINGFIXTURE FOR TWIST DRILLS Clyde E. Cooprider, RR. 1, Rochelle, Ill. 61068Continuation-impart of application Ser. No. 386,299, July30, 1964. Thisapplication July 30, 1965, Ser. No. 476,027

1 Claim. (Cl. 51238) ABSTRACT OF THE DISCLOSURE A fixture attachable tothe steady rest of a wheel type grinder including a generally flat platehaving a plurality of upstanding flanges inclined relative to theforward edge of the plate at a conventional drill tip angle. Theopposite end of the plate is stepped to provide fulcrums differentlyspaced from the front edge of the plate and providing fnlcrums foraccommodating different lengths of drills during sharpening.

This application is a continuation-in-part of my copending applicationSer. No. 386,299, filed July 30, 1964.

This invention relates to a fixture for facilitating the sharpening oftwist drills and the primary object is to provide a fixture which is ofnovel and exceedingly simple construction, adapted to be clamped to therest of an ordinary grinder, locate each cutting edge of a drill beingsharpened relative to the periphery of the grinder, and acourately guidethe manually actuated movements of the drill to effect the sharpeningand formation of the desired relief on the cutting edge.

A more detailed object is to provide for locating the drill tip relativeto the grinding wheel and provide for locating and guiding of the tip byengagement of the drill shank with three surfaces on a simple angle barclamped to the tool rest of the grinder.

. Another object is to adapt the fixture for handling a wide variety ofsizes and diameters of drills.

A further object is to provide for easy sharpening of drills of smalldiameter.

.Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which FIGURE 1 is a fragmentary perspectiveview of a standard bench grinder equipped with a sharpening fixtureembodying the novel features of the present invention.

FIG. 2 is a fragmentary plan vie FIG. 3 is an end view taken along theline 3-3 of FIG. 2.

FIG. 4 is a fragmentary section taken along the line 4-4 of FIG. 2.

FIG. 5 is a left side view.

The improved'fixture is intended for use with a so-called bench grinderhaving a housing in which a shaft 11 is journaled intermediate its endsand carries at one end a grinding wheel in the form of a disk 12 ofbonded abrasive. A bracket swingable on a pivot 13 is clamped against avertical surface 14 on the housing and has at its upper end a plate 16which projects laterally and horizontally across the cylindricalperiphery 17 of the grinding wheel. The plate may be swung about thehorizontal pivot 13 formed bythe clamp screw and thus located atdifferent desired angles according to the angle at which the work is tobe disposed during grinding thereof.

The fixture constituting the present invention comprises a rigid plate20 adapted to be clamped at its forward end against the top of the restplate 16 of the grinder and having a fiat top surface 21 cooperatingwith an upstanding perpendicular guide flange 22 along one side 26against which the drill 23 is held and guided while a cutting edge 24 isbeing sharpened by upward swinging of the drill shank about a fulcrum 36normal to the guide surface 26 and spaced from the tip of the drill adistance less than the length of the drills to be sharpened. The plate20 and the flange 22 may be those of a standard right angle bar ofappropriate size or the entire fixture may be a single piece molding ofany suitable material.

To facilitate clamping of the fixture detachably and in proper angularposition against the top of the tool rest 16, a flat arm 25 constitutingan extension of the bottom plate 20 projects laterally from the forwardend of the plate and, by means of an ordinary screw type C clamp 27, thearm 25 may be fastened detachably against the top of the rest plate 1-6in a position to locate the guide surface 26 properly relative to thegrinding wheel as shown in FIGS. 1 and 2.

To establish the angle 28 relative to the drill axis 21 at which eachcutting lip or edge 24 of the drill. is to be disposed during thesharpening operation, the forward edge 29 of the plate 20 is disposed atan included angle 30 relative to the guide surface 26 equal to the angle28. In most standard drills for use on materials such as steel, thisangle is 59 degrees. Preferably the end 29 extends across the full widthof the bottom plate and arm 25. By clamping the plate 20 to the restplate 16 of the grinder with the edge 29 parallel to the inner edge 31of the tool rest, the side guide surface 26 is inclined relative to theplane of the grinding wheel at the conventional angle 30 of 59 degreesto which the cutting edges 24 of the drill are to be disposed aftersharpening. The plate is positioned along the rest 16 so that the end ofthe drill is disposed between the sides of the grinding wheel forcontact of the full width of the cutting edges 24 with the periphery 17of the wheel.

In accordance with the present invention, each cutting edge of the drillis ground away and sharpened by positioning the drill in the rightangular seat formed by the top 21 of the base plate 20 and the flange 22and then rocking the drill upwardly about the fulcrum 36 which isdisposed intermediate the ends of the drill and extends perpendicular tothe guide surface 26. Herein, this fulcrum is defined by the outer endof the bottom plate 20. It is spaced from the inner end 29 of the seat21, 26 a distance such that as an incident to the upward swinging of thedrill with one cutting edge 24 pressed against the wheel periphery 17, arelief surface 32 (FIG. 4) at the proper angle will be formed on thedrill tip behind the sharpened cutting edge. The relief angle may varyconsiderably without interfering with the cutting efficiency of thedrill so that the fixture as described above and of a given length willaccommodate a substantial range of drill lengths.

To sharpen a drill, the tool rest 16 of the grinder is disposedsubstantially horizontally and the arm 25 is clamped against the rest asshown with the end edge 29 of the plate 20 parallel to the inner edge 31of the rest and the inner end of the side 26 of the guide flange spacedfrom the left side of the grinding wheel a distance greater than theradial length of the cutting edges 24 on the drill to be sharpened. Thedrill is placed firmly, as shown in full in FIGS. 2 and 4 and in phantomin FIG. 1, in the right angular seat formed by the guide surface 26 andthe top of the plate 20 and turned about its axis 21 until one of thelips or cutting edges 24 is disposed horizontally. Then the drill ispushed forwardly to bring the cutting edge 24 into contact with thewheel periphery 17 to remove an amount of stock suflicient to sharpenthe edge. With the drill end held pressed against the wheel periphery,the drill is rocked upwardly about the fulcrum 36 as shown in phantom inFIG. 4 while holding the side of the drill firmly against the side 26 ofthe guide flange 22. The extent of this upwardly swinging is sufiicientto include the full circumferential width of the relief surface 32.

The same procedure is followed in sharpening the second cutting edge ofthe drill. In order to determine the extent of stock removed in thesharpening of the two edges and check the uniformity in the radiallengths of these edges, scale graduations 34 are formed along the outeredge 35 of the arm 25, this edge being disposed parallel to the forwardedge 29 of the plate, Also, the edge is disposed relative to the guidesurface 26 of the guide flange 22 opposite the guide surface at an angle38 which is the complement of the angle 28, that is, at an angle of 121degrees. Herein, this angle is defined by the edge 35 and the outer sideface 39 of a narrow flange 40 lying in the plane of the plate 20 andalong the outer side of the flange 22. By laying the sharpened drillagainst the surface 39 as shown in phantom in FIG. 2 with the sharpenededges disposed successively in abutment with the scale surface 35, theradial lengths of the two edges maybe compared thus determining whetherthese lengthsare equal and whether more stock should be removed from oneof the edges to equalize their lengths and thus make the intersection ofthese edges coincident with the axis of the drill.

The upper edge of the flange 22 is contoured for use in checking theextent of the relief or clearance formed on and around the surface 32 ina sharpening operation as above described. For this purpose, the upperedge of the flange 22 is cut away to form a surface 41 parallel to thetop surface 2 1 and the drill in the starting position (FIG. 4). Anupwardly inclined edge 42 is formed at the inner end of the edge 41making therewith an included angle 43 of 126 degrees which is thedesired five degrees greater than the 121-degree angle 50 that isincluded between cutting lip 24 and the drill axis after sharpening. Bylaying the sharpened drill along the edge 41 with the heel -1 of theclearance face 32 disposed in the plane of the edge 42, this heel willlie substantially in full abutment with the edge 42 if the correctrelief has been formed on the face 32. It will be observed that theamount of such relief formed in the sharpening operation is determinedby which of the fulcrums 36 is used in the pivoting of the drill andalso by the extent of the upward swinging. By selecting the propercombination of these factors, the proper heel clearance can be achieved.

In another of its aspects, the invention contemplates the addition ofone or more additional angular seats 21, 26 of the character abovedescribed but made of narrow widths and shorter lengths to betteraccommodate drills of smaller diameters and shorter lengths. In thepresent instance, two additional seats 21', 26 and 21", 26" are providedby enlarging the base plate 20, providing additional upstanding rightangular flanges 22', 22" thereon. The forward edges 29, 29" of the seatbottoms 21' 21" are continuations of the edge 29 and alined therewith.The seats are made shorter by stepping the fulcrum edges 36, 36" closerto the edge 29. Also, by spacing the flanges 22', 22" differentdistances from the adjacent flange, the seats 21, 26' and 21", 26" maybe made narrower thus enabling the base plate 20 to be made of minimumwidth while still accommodating the desired number of parallel seats.Selection of the angular seat to be used in guiding the sharpening of aparticular drill is usually determined by the length of the drill, theseat selected being substantially shorter than the length of the drillshank as illustrated in phantom in FIG. 2.

In still another of its aspects, the invention contemplates theformation of the base plate 20 of another type of fixture indicatedgenerally at 45 for supporting drills 46 of very small diameters, forexample, less than oneeighth inch, and sharpening the cutting edgesthereof with a flat instead of a round clearance face disposed at asatisfactory clearance angle of, for example, 12 degrees. For thispurpose, a flange 47 is cast integral with the base plate 20 to the leftof the flange 22" and the portion 21 thereof with the top of the flangeinclined forwardly and upwardly relative to the plate at the desiredclearance angle 48, such as 12 degrees, to be formed in sharpening smalldiameter drills. To receive the shanks of such drills and hold thelatter in position to sharpen the cutting edges at the desired 59-degreeangle, the top of the flange is formed with a groove 49 of V- shapedcross-section in which the shank of the small size drill is held firmlyseated during sharpening.

To sharpen such a small drill, the base plate 20 is shifted along therest 16 and clamped to the latter with the groove 49 intersecting theperiphery 27 of the grinding wheel. Then, with one cutting edge of thedrill disposed horizontally as before, it is only necessary to advancethe drill along the groove 49 and into contact with the grinding wheelperiphery. This procedure is repeated after turning the drill in thegroove to present the other cutting edges in proper sharpening position.

It will be apparent that the present sharpening fixture, althoughextremely simple in structure and operation, is capable, even when usedby an unskilled operator, of effecting the sharpening of conventionaldrills of all sizes and lengths with an accuracy sufficient for mostdrilling operations. The accuracy achieved has been found to approachclosely that achieved by costly automatic drill sharpening machines.

I claim as my invention:

1. A fixture for sharpening twist drills of different sizes and lengthscomprising a base plate, a plurality of parallel guide flangesupstanding from the plate and laterally spaced apart to receive betweenthem different drills to be sharpened, means by which one end of saidplate may be clamped against the horizontal tool rest of a grinder anddisposed in front of and extending across the periphery of the grindingwheel with said flanges disposed vertically and the end of said plateadjacent said wheel disposed at an included angle relative to the planesof said guide flanges equal to the angle included between the lip andaxis of the drills to be sharpened, and a plurality of steps formed onthe opposite end of said plate adjacent the respective flanges and eachextending crosswise substantially at right angles to said flanges butspaced different distances from said first plate end whereby to formfulcrums for guiding the upward swinging of the tip of the drills ofdifferent lengths while the lips of the respective drills, when beingsharpened individually, are in contact with said wheel periphery and theside of the drill is held against the adjacent one of said guideflanges.

References Cited 7 UNITED STATES PATENTS 288,069 11/1883 Landers 51219 X1,052,073 2/1913 Mallory 51--219 1,920,537 8/1933 Ward 51-239 1,944,5401/1934 Bailey 51219 2,800,755 7/1957 Perra 5l-219 X 3,089,290 5/ 1963Warm-Reithmayer 51219 X 3,121,983 2/1964 English 51-219 HAROLD D.WHITEI-IEAD, Primary Examiner,

